In terms of availability, it is really only available whenever Ian runs a GB, so I'm not sure if I would describe it as 'readily available' though I can't see Ian having a huge objection to someone replicating the PCB since it is relatively simple. A similar circuit could be made on board though the QFN package reg chip isn't as simple (though it certainly is possible) to solder with conventional soldering iron so might not be ideal as the 'default' but it does represent a significant step up in performance over the ADP150.